Steam Cracking with Supplemental Electrical Heating

ABSTRACT

A hybrid steam cracking process including, in addition to combusting a fuel in a steam cracker furnace to provide thermal energy to the radiant and convection sections, heating a segment of an external furnace piping using an electrical heating device. The external furnace piping can include, e.g., the hydrocarbon-containing feed inlet piping, the cross-over piping, the radiant section inlet piping, and the radiant section outlet piping. Capacity and selectivity of the steam cracker furnace can be enhanced compared to conventional steam cracking process without electrical heating. The technology can be conveniently deployed in existing conventional steam cracking facilities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Application No. 63/222,311 having a filing date of Jul. 15, 2021, and U.S. Provisional Application No. 63/271,927 having a filing date of Oct. 26, 2021, the disclosures of both of which are incorporated herein by reference in their entireties.

FIELD

Embodiments of the present disclosure generally relate to processes and systems for steam cracking hydrocarbons. In particular, the present disclosure relates to steam cracking processes and systems for cracking hydrocarbons for producing hydrocarbon products such as olefins using an electrical heating device to provide thermal energy to an external furnace piping segment, in addition to providing thermal energy to the steam cracking furnace by combusting a fuel.

BACKGROUND

Steam cracking refers to a commercial process for the production of light olefins, especially ethene and propene. In typical steam cracking processes, the hydrocarbon feed is first preheated and mixed with dilution steam in the convection section of the furnace. After preheating in the convection section, the vapor feed/dilution steam mixture is rapidly heated in the radiant section to achieve thermal cracking of hydrocarbons. After a predetermined amount of thermal cracking occurs, the furnace effluent is rapidly quenched in either an indirect heat exchanger or by the direct injection of a quench oil stream. Significant amount of thermal energy is needed to meet the heating in the conventional and radiant sections, which conventionally is provided by combusting a fuel, e.g., a hydrocarbon-containing fuel, at a plurality of burners located inside the furnace. The combustion of hydrocarbon produces a flue gas comprising CO₂ typically emitted into the atmosphere. The discharge of the flue gas also results in loss of a portion of thermal energy to the atmosphere. There is a need to reduce emissions and loss of thermal energy to the atmosphere.

A byproduct of the cracking process includes carbon deposits, referred to as “coke,” on the inner surfaces of the radiant tubes of the furnace. Depending on the feedstock being cracked, coke may also be deposited in certain tubes in the convection section, or in the quench system of the furnace. Decoking operations can impact cracking throughput. There is a need to lengthen the production operation between two adjacent decoking operations. There are also needs for increasing furnace conversion, selectivity, and capacity. Conventional steam cracking using solely thermal energy produced by combusting a steam cracker fuel for the convection and radiant sections need improvement to satisfy one or more of these needs.

SUMMARY

A first aspect of this disclosure relates to a process for steam cracking a hydrocarbon-containing feed, the process comprising one or more of the following: (I) providing a steam cracking furnace comprising one or more of the following: a furnace enclosure, a plurality of burners housed in the furnace enclosure capable of supplying thermal energy by combusting a fuel, a hydrocarbon-containing feed inlet tube located outside of the furnace enclosure capable receiving a hydrocarbon-containing feed, a convection section located inside the furnace enclosure and coupled to the hydrocarbon-containing feed inlet tube, a cross-over section located outside of the furnace enclosure and coupled to an end of the convection section, a radiant section located inside the furnace enclosure and coupled to an end of the cross-over section via a radiant section inlet piping, a radiant section outlet piping coupled to the radiant section and located outside of the furnace enclosure, and one or more electrical heating devices capable of providing heat energy to an external furnace piping selected from: a segment of the hydrocarbon-containing feed inlet tube, a segment of the cross-over section, a segment of the radiant section inlet piping, and a segment of the radiant section outlet piping, and combinations thereof; wherein the radiant section inlet piping is located outside of the furnace enclosure; (II) combusting the fuel at the plurality of the burners to provide thermal energy to the radiant section and the convection section; (III) supplying electrical power to at least one of the one or more electrical heating devices to provide heat energy to the segment of the external furnace piping; and (IV) in a cracking mode, feeding the hydrocarbon-containing feed through the hydrocarbon-containing feed inlet tube and optionally water and/or steam into the steam cracking furnace, heating the hydrocarbon-containing feed and/or the water/steam in the convection section to obtain a heated feed mixture, transferring the heated feed mixture from the convection section to the radiant section via the cross-over section and the radiant section inlet piping, cracking a plurality of hydrocarbons in the heated feed mixture in the radiant section to produce a cracked mixture exiting the steam cracking furnace through the radiant section outlet piping.

A second aspect of this disclosure relates to process for steam cracking a hydrocarbon-containing feed, the process comprising one or more of the following: (I) providing a steam cracking furnace comprising one or more of the following: a furnace enclosure, a plurality of burners housed in the furnace enclosure capable of supplying thermal energy by combusting a fuel, a hydrocarbon-containing feed inlet tube located outside of the furnace enclosure capable receiving a hydrocarbon-containing feed, a convection section located inside the furnace enclosure and coupled to the hydrocarbon-containing feed inlet tube, a cross-over section located outside of the furnace enclosure and coupled to an end of the convection section, a radiant section located inside the furnace enclosure and coupled to an end of the cross-over section via a radiant section inlet piping, a radiant section outlet piping coupled to the radiant section and located outside of the furnace enclosure, and one or more electrical heating devices capable of providing heat energy to an external furnace piping selected from: a segment of the hydrocarbon-containing feed inlet tube, a segment of the cross-over section, a segment of the radiant section inlet piping, and a segment of the radiant section outlet piping, and combinations thereof; wherein the radiant section inlet piping is located outside of the furnace enclosure; (II) combusting the fuel at the plurality of the burners to provide thermal energy to the radiant section and the convection section; (III) supplying electrical power to at least one of the one or more electrical heating devices to provide heat energy to the segment of the external furnace piping; and (VIII) in a decoking mode, feeding a decoking fluid into the radiant section; wherein step (III) comprises supplying electric power to at least one electrical heating device capable of providing heat energy to a segment of the radiant section inlet piping.

These and other features and attributes of the disclosed apparatus of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments.

FIG. 1 is a schematic illustration of a steam cracking furnace of this disclosure comprising one or more electrical heating devices coupled to one or more segments of external furnace piping(s), in accordance with some embodiments.

FIG. 2 is a schematic illustration of a cross-sectional end view of an insulated electrical heating device coupled to a segment of an external furnace piping of a steam cracking furnace, in accordance with some embodiments of this disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

Steam cracking furnace performance can be limited by build-up of coke inside radiant tubes of the furnace. The coke acts as a thermal insulator resulting in increasing radiant tube metal temperatures (TMTs) as a run progresses. Once the TMTs approach or reach the design limit, the furnace needs to be decoked.

The coke inside the tubes also causes a hydraulic restriction and higher coil pressure drop. When the pressure drop becomes high enough, the resulting higher backpressure causes a loss-of-critical-flow at the flow nozzles located at the inlet of the radiant section. Once critical flow is lost for a particular tube, the flow rate through that tube will be reduced which results in a higher coking rate, which aggravates the hydraulic restriction further. This cycle continues rapidly and a decoke operation will be required.

Reducing the radiant tube metal temperatures typically has an impact on throughput and production. One method for reducing the radiant TMTs is to raise the process duty of the furnace convection section so that the required radiant duty is lower for a given feed rate, steam to hydrocarbon ratio, and conversion. Raising the duty of the convection section raises the temperature of the process gas leaving the convection section. The temperature of the process gas leaving the convection section is referred to as the cross-over temperature (“XOT”, not to be confused with the term used in industry to denote radiant coil outlet temperature “COT”).

In some steam cracking operations, it is believed that temperatures in the convection section should be limited such that any significant thermal cracking does not occur therein. This belief is based on the assumed drawbacks that (1) thermal cracking in the convection section or cross-over piping is not adequately selective for certain products such as ethene, and (2) that it will cause coking inside the convection section tubes. It has been discovered that raising the XOT such that some amount of thermal cracking occurs in the convection section and the cross-over piping reduces radiant section TMTs with reduced or eliminated drawbacks of reduced product selectivity and coking inside the convection section tubes. A high XOT is used to increase the time between decoking operations for certain fixed conditions such as feed rate, steam to hydrocarbon ratio, conversion, among others. In some aspects, certain conditions can be further improved, such as increasing feed rate and/or conversion while maintaining similar TMT and/or furnace run-length.

For existing steam crackers, increasing XOT across a specific operating mode can be difficult without changing the furnace design, without increasing emissions to the environment, and while considering operating conditions for different operating modes, such as cracking mode and decoking mode.

FIG. 1 schematically illustrates a steam cracking furnace 101 operating in cracking mode. The furnace 101 includes: a furnace enclosure 103, a plurality of burners 102 housed in the furnace enclosure capable of supplying thermal energy by combusting a fuel, a hydrocarbon-containing feed inlet tube 105 located outside of the furnace enclosure 103 capable receiving a hydrocarbon-containing feed, a convection section 109 (including segments 109 a and 109 b) located inside the furnace enclosure 103 and coupled to an end of the hydrocarbon-containing feed inlet tube 105, a cross-over section 115 located outside of the furnace enclosure and coupled to an end 111 of the convection section 109, a radiant section 104 located inside the furnace enclosure (including multiple radiant tubes 104 a, 104 b, . . . ) and coupled to an end 119 of the cross-over section 115 via a radiant section inlet piping 120, a radiant section outlet piping 131 coupled to the radiant section 104 and located outside of the furnace enclosure 103, and one or more electrical heating devices 106, 113, 117, 118, 123, 127, and 133 capable of providing heat energy to an external furnace piping selected from: a segment of the hydrocarbon-containing feed inlet tube 105, a segment of the cross-over section 115, a segment of the radiant section inlet piping 120, and a segment of the radiant section outlet piping 131, and combinations thereof; wherein the radiant section inlet piping 120 is located outside of the furnace enclosure 103. A fuel is supplied to the plurality of burners 102, where it is combusted to provide thermal energy to the radiant section 104 and the convection section 109. Electrical power is supplied to at least one of the one or more electrical heating devices 106, 113, 117, 118, 123, 127, and 133 to provide heat energy to the external furnace piping. During cracking mode of the steam cracking furnace, the hydrocarbon-containing feed through the hydrocarbon-containing feed inlet tube 105 and optionally water and/or steam through inlet tube 107 are supplied into the steam cracking furnace, which are first heated in the convection section to obtain a heated feed mixture. The heated feed mixture from the convection section is then supplied to the radiant section 104 via the cross-over section 115 and the radiant section inlet piping 120. Inside the radiant section 104, a plurality of hydrocarbons in the heated feed mixture undergo cracking reactions to produce a cracked mixture exiting the steam cracking furnace through the radiant section outlet piping 131. The hydrocarbon-containing feed can include carbon-containing materials such as ethane, propane, butane, naphtha, gas oil, crude oil, or combination(s) thereof.

I. Electrical Heating a Segment of the Hydrocarbon-Containing Feed Tube

In some embodiments, the hydrocarbon-containing feed inlet tube 105 is disposed outside the furnace enclosure 103 and a segment thereof is heated electrically by the electrical heating device 106. The thus heated inlet tube heats the hydrocarbon-containing feed therein before it enters the convection section of the tube in the furnace enclosure 103. In certain situations where electrical heating to the feed inlet tube 107 is not desired, the electrical heating device 106 may be not installed, or turned off. Desirably the heating power of the electrical heating device 106 is controllable and adjustable to suit the needs of various hydrocarbon-containing feeds at differing operation periods. As a result of electrical heating provided by device 106, the hydrocarbon-containing feed stream in the inlet tube 105 can have a temperature increase across the segment heated by device 106 of from, e.g., 1, 2, 4, 5, 6, 8, 10, to 15, 20, 25, 30, 40, 45, 50, to 55, 60, 65, 70, 75, 80, 85, 90, 95, to 100, 120, 130, 140, 150, to 160, 170, 180, 190, 200° C. Preferably, at least a portion of the electrical power supplied to device 106 is produced by a renewable source such as a wind turbine-driven generator or a solar cell, or a combination thereof. Heating the hydrocarbon-containing feed stream in tube 105 using the electrical heating device 106 can reduce the heat duty required from the burners 102 in the furnace, thereby curtailing the amount of hydrocarbon-based fuel consumed in the steam cracker.

In an upper section 109 a of the convection section 109, the hydrocarbon-containing feed stream is heated by, e.g., the flue gas produced by the combustion of a steam cracker fuel at the burners 102. A diluent steam stream is fed into a lower portion 109 b of the convection section 109 via a steam inlet tube 109 to mix with the hydrocarbon-containing feed to form a hydrocarbon/steam feed stream. The combined hydrocarbon/steam feed stream travels downward along the convection section 109 and is further heated by the flue gas produced from the combustion at the burners 102. An end 111 of the convection section 109, typically located outside of the furnace enclosure 103, is coupled to an end of the cross-over section 115 typically located outside of the furnace enclosure 103.

The temperature of the fluid stream inside the convection section 109 may be controlled at a temperature below the reaction temperature for cracking of hydrocarbon to reduce the degree of cracking within the convection section. Alternatively, the temperature in the convection section 109, especially the downstream portion thereof close to the end 111, may be controlled at a level sufficiently high to allow significant cracking to occur therein, as is described in U.S. Pat. No. 10,315,968. The temperature of the fluid in the convection section can be advantageously controlled/adjusted by using the electrical heating device 106. By heating the hydrocarbon-containing feed supplied to the inlet tube 105 using electrical heating device 106, one can achieve a desirable temperature of the fluid at the end 111 of the convection section, with or without adjusting the thermal energy output of the burners 102. Heating the hydrocarbon-containing feed stream in tube 105 using the electrical heating device 106 can reduce the heat duty required from the burners 102 in the furnace, thereby curtailing the amount of hydrocarbon-based fuel consumed in the steam cracker, and reducing energy loss from increase amount of flue gas exiting the top of the furnace. Without using the electrical heating device, in order to increase the temperature of the fluid in the convection section 109, one would have to increase thermal energy output of the burners 102, which can result in higher temperature of the downstream tubes 104 a and 104 b in the radiant section 104, causing an undesirably high rate of coking and reduced run length of the radiant tubes.

II. Electrical Heating a Segment of the Cross-Over Section

In addition to and/or in lieu of the electrical heating of the hydrocarbon-containing feed piping described in Section I above, electrical heating may be used to heat a segment of a cross-over section piping. As shown, in some embodiments, one or more electrical heating devices (e.g., 113, 117, and 118) is coupled to one or more segments of the cross-over section 115, capable of providing thermal energy to the segment(s) if electrical power is supplied thereto. In some embodiments, an electrical heating device 120 is coupled to a segment of the cross-over section 113 proximate to end 111, and/or an electrical heating device 117 is coupled to a segment of the cross-over section 113 in the middle, and/or an electrical heating device 118 is coupled to a segment of the cross-over section 113 in proximity to end 119. The operation of any of the electrical heating devices 113 and/or 117 and/or 118, by supplying electrical power thereto, is capable of separately and independently raising the temperature of each of the coupled segments of the cross-over section by tb ° C., where tb can range from, e.g., 0, 2, 4, 5, 6, 8, 10, to 20, 30, 40, 50, 60, to 70, 80, 90, 100, to 110, 120, 130, 140, 150, to 160, 170, 180, 190, or 200, depending on, e.g., the initial temperature of the hydrocarbon-containing feed/steam mixture at the end of the convection section, the degree of desired cracking that may occur in the cross-over section, and the metallurgy of the metal used for the cross-over section. In certain embodiments, the one or more electrical heating devices may be coupled and capable of providing thermal energy to, e.g., from 10%, 20%, 30%, 40%, to 50%, 60%, 70%, 80%, to 90%, 95%, or even 100% of the total length of the cross-over section 115.

In the absence of active heating provided to the cross-over section 115, the temperature of the fluid stream inside the cross-over section 115 would decrease from end 111 to end 119. With the active heating provided by electrical heating device 113 and/or 117 and/or 118 to one or more segments, the fluid stream inside the cross-over section can increase from end 111 to end 119 by tc ° C., where tc can range from e.g., 0, 2, 4, 5, 6, 8, 10, to 20, 30, 40, 50, 60, to 70, 80, 90, 100, to 110, 120, 130, 140, 150, to 160, 170, 180, 190, or 200. As a result of the active heating by one or more of heating devices 113 and/or 117 and/or 118, the temperature of the fluid in the cross-over section 115 may reach a level such that significant cracking of hydrocarbons may occur in the cross-over section, even though such cracking may be negligible at the upstream end 111. Desirably, at least one, preferably all of the electrical heating devices coupled to the various segments of the cross-over section 115 are controllable and adjustable, preferably individually and separately controllable and adjustable, to provide various levels of thermal energy output to the cross-over section 115. One or more temperature monitoring devices (e.g., thermocouples) may be installed to monitor the temperatures of the cross-over section at various locations and/or the temperatures of the fluid inside the cross-over section at various locations. The measured temperature(s) may be advantageously used to control the heating power output of one or more of the electrical heating devices coupled with the various segments of the cross-over section, so that desirable temperatures of the fluid inside the cross-over section at various locations can be controlled and adjusted. Preferably, at least a portion of the electrical power supplied to device 113 and/or 117 and/or 118 is produced by a renewable source such as a wind turbine-driven generator or a solar cell, or a combination thereof. Heating the hydrocarbon-containing feed stream in cross-over section 115 using the electrical heating device 113 and/or 117 and/or 119 can reduce the heat duty required from the burners 102 in the furnace, thereby curtailing the amount of hydrocarbon-based fuel consumed in the steam cracker, and accordingly reducing the amount of CO₂ emission into the atmosphere.

The setup of a typical steam cracker is described in U.S. Pat. No. 10,316,968 B2. The end of the convection section is connected to the start of the cross-over section 111 of the steam cracking tube, the fluid stream therein has a temperature of T1 ° C. The cross-over section is typically located outside of the wall of the furnace to avoid heating the hydrocarbon and steam mixture to an exceedingly high temperature where substantial cracking can occur prematurely. At the end of the cross-over section 119, a second fluid stream at T2 ° C. is obtained. The cross-over section is thermally insulated to prevent excessive heat loss with or without active heating. Where no active heating is applied, T2 is typically slightly lower than T1 as a result of heat loss and/or endothermal cracking reactions occurring if T1 is sufficiently high.

By raising fluid temperature inside the cross-over section with an electric heating device, the following can be achieved: (a) increasing furnace capacity at a constant emissions limit by raising feed rate and/or conversion while maintaining a similar TMT and/or furnace runlength; or (b) maintaining existing furnace capacity and lowering onsite furnace emissions by lowering the required duty in the radiant section while maintaining a similar TMT and/or furnace runlength. The active heating of the cross-over section using the electrical heating device can result in T2>T1. In this scenario, coil inlet temperature may be raised or lowered independently of furnace firing. This allows for the increase in XOT to be achieved independently of furnace design or configuration.

The use of an electrical heating device to heat one or more segments of the cross-over section changes the heat balance of a conventional steam cracker. In a conventional steam cracker without using electrical heating, the radiant section and convection section are heat integrated. Cross-over temperature is therefore dependent on the flow through the convection section and flue gas conditions in the radiant section entering the convection section. By applying an electrical source to the unfired cross-over piping, this heat balance is partially decoupled. This has the following advantages: (a) one can increase or decrease XOT independently of radiant section and convection section conditions (flow rates, furnace firing, and the like) by increasing or decreasing the amount of electric heat applied; (b) rendering the source of emissions from the electric heating to be independent of the furnace operation, enabling the use a reduced emission source or a non-local low-emission source to supply the electrical heating; (c) making independent, precise control of individual cross-over pass temperatures possible to suit the needs of individual furnace passes or during different furnace operating modes.

Individual furnace pass control may be advantageous during certain furnace operations. This may include where specific cross-over temperature targets cannot be achieved by a single furnace designs. In these cases it may be desirable to change the heat balance to the cross-over (by supplementing with electrical energy) during decoking, feed operation, or changes between feeds. In addition if a specific temperature target is desired during a specific operating mode, heat may be applied or removed such that each cross-over pass can precisely achieve the temperature target. This may be performed by monitoring the heat input to the cross-over line by taking the differential temperature between T1 and T2. In this way, a specific value of T2 may be achieved to each individual cross-over pass.

III. Electrical Heating of a Segment of Radiant Section Inlet Piping

In addition to and/or in lieu of the electrical heating of the hydrocarbon-containing feed piping and the cross-over section piping described in Sections I and II above, electrical heating may be used to heat a segment of a cross-over section piping. At the end of the cross-over piping, prior to entry into the radiant firebox, many furnaces have small sections of radiant tube protruding from the firebox. Similar to the cross-over section—these sections can be heated by using electrical heating to achieve similar benefits. Further, with electrical controls that enable different current input to each tube, the electrical heating could be adjusted to each tube to provide the same coil outlet temperature or same conversion or same coking in each tube with adjustment based on coil outlet temperature only or preferably the tube-by-tube measurement capabilities as described in patent application WO201913325A1.

As shown in FIG. 1 , the radiant section 104 includes a plurality of radiant tubes (104 a, 104 b, . . . ). The radiant section 104 is coupled to an end 119 of the cross-over section 113 via a radiant section inlet piping 120, which can include a connection tube coupled to end 119 of the cross-over section 119, one or more manifolds, and a plurality of connection tubes coupled to ends of a plurality of radiant tubes 104 a and 104 b, as shown in FIG. 1 . One or more electrical heating devices (e.g., 123 and 127 as shown) may be installed to provide thermal energy to one or more locations of the radiant section inlet piping. For example, an electrical heating device may be coupled to the manifold of the radiant section inlet piping and operated to provide thermal energy thereto, thereby heating the fluid inside the manifold, which is subsequently distributed to all radiant tubes. In preferred embodiments, separate electrical heating devices (e.g., 123 and 127 as shown) may be installed and operable to provide thermal energy to the separate connection tubes coupled to individual radiant tubes, or to the inlet ends of the separate radiant tubes, such that the fluid entering into the individual radiant tubes can be individually and separately heated. Desirably, at least one, preferably all of the electrical heating devices coupled to the various segments of the radiant section inlet piping are controllable and adjustable, preferably separately and individually controllable and adjustable, to provide various levels of thermal energy output. One or more temperature monitoring devices (e.g., thermocouples) may be installed to monitor the temperatures of the radiant inlet piping at various locations and/or the temperatures of the fluid inside the radiant section inlet piping at various locations. The measured temperature(s) may be advantageously used to control the heating power output of one or more of the electrical heating devices coupled with the various segments of the radiant section inlet piping, so that desirable temperatures of the fluid inside the radiant section inlet piping at various locations, and the desirable temperatures of the fluid streams entering the individual radiant tubes, can be controlled and adjusted. The temperature of the segment of the radiant section inlet piping heated by the electrical heating device (e.g., 123 and/or 127) can be raised by Td ° C. as a result of the thermal energy released by the electrical heating device. Depending on, e.g., the type of the hydrocarbon-containing feed, and the temperature of the fluid at end 119 of the cross-over section 115, Td can range from, e.g., 1, 2, 4, 5, 6, 8, 10, to 15, 20, 25, 30, 40, 45, 50, to 55, 60, 65, 70, 75, 80, to 85, 90, 95, 100, 110, 120, to 130, 140, 150, 160, 170, 180, 190, 200. As a result of electrical heating provided by device 123 or 127, the fluid stream in the radiant section inlet piping can have a temperature increase across the segment heated by the device of from, e.g., 1, 2, 4, 5, 6, 8, 10, to 15, 20, 25, 30, 40, 45, 50, to 55, 60, 65, 70, 75, to 80, 85, 90, 95, 100° C. Preferably, at least a portion of the electrical power supplied to device 123 and/or 127 is produced by a renewable source such as a wind turbine-driven generator or a solar cell, or a combination thereof.

Preferably, at least a portion of the electrical power supplied to device 123 and/or 127 is produced by a renewable source such as a wind turbine-driven generator or a solar cell, or a combination thereof. Heating the hydrocarbon-containing feed stream in radiant section inlet piping 120 using the electrical heating device 123 and/or 127 can reduce the heat duty required from the burners 102 in the furnace, thereby curtailing the amount of hydrocarbon-based fuel consumed in the steam cracker, in addition to individually and separately controlling and/or adjusting the temperature inside the radiant tubes.

The radiant tubes 104 a, 104 b, . . . in the radiant section 104 are typically heated by thermal energy released from a series of combustion flames generated by a plurality of burners 102. Depending on the locations of the radiant tubes and the burners, uneven amount of thermal energy may be received by the plurality of radiant tubes from the flames, resulting in temperature variations, and thus variations of hydrocarbon conversion, and thus variations of coking rates, among the radiant tubes. By providing separate electrical heating to the connection tubes in the radiant section inlet piping to the radiant tubes, one can adjust the temperatures inside the radiant tubes to achieve desired temperature, desired hydrocarbon conversion, and desired coking rate in them, effectively compensating the variation of heating provided by the flames. Better control of the steam cracking process can be thus achieved.

IV. Electrical Heating of a Segment of Radiant Section Outlet Piping

In addition to and/or in lieu of the electrical heating of the hydrocarbon-containing feed piping, the cross-over section piping, and the radiant section inlet piping described in Sections I, II, and III above, electrical heating may be provided to the radiant section out piping.

In conventional steam cracker without electrical heating, when the cracked fluid mixture leaves the radiant section coil, it enters a small section of unfired outlet piping. The cracked fluid mixture stream continues to the quench exchanger where it is quickly cooled and subsequently separated to obtain the desired product fractions. This effluent exits the radiant firebox at temperature T3, commonly referred to as coil outlet temperature (COT). After a brief period of residence time in the unfired outlet piping, it enters the quench exchanger at T4, referred to as quench inlet temperature.

It is known in industry that the length of this unfired radiant outlet should be minimized. Ideally the cracked fluid mixture exiting the radiant firebox should be quenched and cooled instantaneously, which is not practical due to the typical layout and spacing required of such large equipment. Therefore, the residence time of the cracked fluid mixture is minimized in this portion of unfired piping. However, due to physical constraints, and depending upon the layout of such a furnace, this cannot be reduced to zero residence time. If residence time is not minimized, secondary reactions occur in the unfired out piping which limit or reduce the selectivity of the cracked fluid mixture toward the desired products. Even in the minimized length of radiant outlet piping, some unselective reactions occur in this region. Older designs of furnaces may have been designed to be less selective than their newer counterparts. Therefore, introducing options to increase their selectively at low cost is beneficial. This section of unfired piping is generally heavily insulated to maintain temperature and considered mostly adiabatic. However, due to the endothermal nature of the cracking reactions occurring, and the result of heat loss despite heavy insulation of this piping section, the cracked fluid mixture enters the quench exchanger at a lower temperature than it exited the furnace firebox. Therefore, T4 is generally slightly lower than T3.

By electrically heating the unfired outlet piping the losses of unselective cracking in this area can be minimized Such introduction of heat to the unfired piping can achieve similar effects of electrical heating of the cross-over section, albeit opposite effects on tube metal temperature. Increasing selectivity allows for increased furnace capacity inside the radiant box. By employing (i) electrically heating the cross-over section as described in Section II, and/or electrical heating the radiant section inlet piping as described in Section III above; and (ii) electrically heating the radiant section outlet piping, increased desirable yields can be provided by (ii) at the cost of increased tube metal temperature which can be offset by the reduction in tube metal temperature resulting from (i).

Inside the radiant section tubes, the fluid is heated to a high temperature to undergo cracking reactions, producing a steam cracker effluent stream exiting the radiant section tubes. The radiant section tubes are coupled at the downstream ends thereof to a radiant section outlet piping 131, which can also include a manifold coupled to ends of multiple radiant tubes on the inlet end and a transfer line tube 135 on the outlet end. Transfer line 135 is coupled to a transfer line heat exchanger/quenching device 137 where the fluid exiting line 135 is rapidly quenched. A steam cracker effluent stream comprising olefins is discharged through tube 135, which may be quenched/cooled downstream to a lower temperature. In certain embodiments, it may be desirable to install an electrical heating device 133 coupled to a segment of the radiant section outlet piping (e.g., a segment of transfer line tube 135, as shown), capable of providing an additional thermal energy to the steam cracker effluent therein, enabling additional desirable cracking in the radiant section outlet piping. The temperature of the segment of the radiant section outlet piping heated by the electrical heating device 133 can be raised by Te ° C. as a result of the thermal energy released by the electrical heating device 133. Depending on, e.g., the type of the hydrocarbon-containing feed, and the temperature of the steam cracker effluent immediately exiting the furnace enclosure 103, Te can range from, e.g., 1, 2, 4, 5, 6, 8, 10, to 15, 20, 25, 30, 40, 45, 50, to 55, 60, 65, 70, 75, 80, 85, 90, 95, to 100, 110, 120, 130, 140, 150, to 160, 170, 180, 190, 200. Desirably the heating power of the electrical heating device 133 is controllable and adjustable to suit the needs of various hydrocarbon-containing feeds at differing operation periods. As a result of electrical heating provided by device 133, the hydrocarbon-containing feed stream in radiant section outlet piping can have a temperature increase across the segment heated by device 133 of from, e.g., 1, 2, 4, 5, 6, 8, 10, to 15, 20, 25, 30, 40, 45, 50, to 55, 60, 65, 70, 75, to 80, 85, 90, 95, 100, to 110, 120, 130, 140, 150° C. Where the heated segment is a segment of the transfer line tube 135 as shown, the heated segment can constitute from, e.g., 10%, 20%, 30%, 40%, 50%, to 60%, 70%, 80%, 90%, 95%, or even 100% of the length of the transfer line tube 135. Preferably, at least a portion of the electrical power supplied to device 133 is produced by a renewable source such as a wind turbine-driven generator or a solar cell, or a combination thereof. Heating the radiant section outlet piping using the electrical heating device 133 can reduce the heat duty required from the burners 102 in the furnace, thereby curtailing the amount of hydrocarbon-based fuel consumed in the steam cracker.

Without active heating provided to the radiant outlet piping, the temperature of the fluid inside the piping decreases along the path due to additional reactions. Without intending to be bound by a particular theory, it is believed that as the temperature of the fluid decreases, undesirable side reactions increases, leading to reduction of selectivity toward desired products such as ethylene. For this reason, in conventional steam crackers without active heating provided to the radiant outlet piping, the steam cracker effluent is typically immediately quenched to reduce the undesirable side reactions in the radiant outlet piping. In an embodiment of the processes of this disclosure where an electrical heating device 133 is used to heat a segment of the radiant outlet piping, the fluid inside the radiant outlet piping can be maintained at a desirably high temperature until it reaches the transfer line heat exchanger/quenching device 137, enabling the continuation of desirable cracking reactions in line 135 and the reduction of undesirable side reactions that would otherwise occur at a lower temperature, thereby achieving a desirable selectivity toward high-value products such as ethylene. Upon cooling/quenching in device 137, a cooled steam cracker effluent exiting device can be separated to recover products such as ethylene, propylene, C4 olefins, C4 dienes, naphtha, and the like.

One or more of the electrical heating devices used in the processes of this disclose (e.g., 113, 117, 118, 123, 127, 133, as shown) can include a resistor separate from and electrically insulated from the external furnace piping. The resistor is capable of receiving at least a portion of electrical power to produce heat energy by resistive heating, which is then transferred to the segment of the external furnace piping. The resistor can take the form of, e.g., a metal wire. In some embodiments, one or more of the electrical heating devices can include a portion of the external piping (which is made of a metal material, e.g., stainless steel), at least a portion of the electrical power can be supplied to the segment of the external furnace piping generating an electric current flowing through the external furnace piping to provide heat energy to the external furnace piping. In some embodiments, at least one of the electrical heating devices is capable of providing heat energy to the external furnace piping by induction heating, such as by inducing an electric current in the external furnace piping. In some embodiments, at least one of the electrical heating devices provides heat energy to the segment of the external furnace piping by radiant heating. In a preferred embodiment, one or more of the electrical heating devices can take a form of a heating jacket at least partially enclosing the external furnace piping. The electrical heating device may be further covered by a layer of thermal insulator to prevent heat loss and raise overall efficiency.

In preferred embodiments, the electrical heating power supplying at least one of the electrical heating devices is adjustable and/or controllable. In some embodiments, a temperature-monitoring device is coupled to the external furnace piping and is capable of determining a temperature of the external furnace piping. A controller may be used to control/adjust the heating power of at least one of the electrical heating devices based on the temperature of the external furnace piping determined by the temperature-monitoring device. For example, the temperature of the external furnace piping may be maintained in a range from T(target)−15° C. to T(target)+15° C., or T(target)−10° C. to T(target)+10° C., or T(target)−5° C. to T(target)+5° C., where T(target) is a predetermined target temperature of the external furnace piping.

FIG. 2 schematically illustrates a cross-sectional end view 201 of an external piping segment coupled to an electrical heating device in various embodiments of this disclosure. As shown, an external furnace piping segment 203 is enclosed by an electrical heating device 205 which advantageously takes the form of a jacket. The electrical heating device 203 can include a resistive electrical heating element (not shown) made of an electrically conductive material having a given electrical resistance. Upon being supplied with electrical power to the electrical heating element, an electrical current passes through it, thereby producing thermal energy. The electrical heating device can further include an electrical insulator (not shown) disposed between the electrical heating element and the external surface of the piping 203 (which is typically made of metal). The thermal energy produced by the electrical heating element can be transferred, through the electrical insulator, to piping 203. The thus heated piping segment can heat a fluid passing through the segment. The electrical heating device 205 can be further enclosed by a thermal insulator layer 207 to prevent heat loss to the environment.

In alternative embodiments, the electrical heating device 205 may include an induction heating device that comprise an electrical winding (not shown). Upon supplying an alternate electrical power to the electrical winding, an alternate electromagnetic field can be generated enclosing the piping 203, thereby inducing electrical current flowing through the metal piping 203, generating thermal energy and heating the piping 203. The thus heated piping 203 can heat a fluid passing through the segment. The electrical heating device 205 can be further enclosed by a thermal insulator layer 207 to prevent heat loss to the environment.

In yet other embodiments, a voltage can be directly applied across at least a portion of the segment 203 to produce an electrical current passing through the segment, thereby heating the segment, in addition to or in lieu of the indirect electrical heating using a resistive heating device or the induction heating device. Likewise, the piping segment 203 may be enclosed by a thermal insulator layer to prevent heat loss to the environment.

In cracking mode, coke may form in the convection section, the cross-over section, and the radiant section. Coke includes hydrocarbons having much higher boiling temperatures than the hydrocarbon feed material and is deposited on the inner surface of the reactor tubes. Buildup of a coke layer over time reduces heat transfer from the tube wall to the fluid stream therein, increases pressure differential from the inlet to the outlet of the tube coil, and leads to reactor wall corrosion by carbonization of the tube material. To offset the reduction of heat transfer resulting from coke deposition, higher tube external wall temperature can be applied, which can increase coke accumulation. A steam cracking furnace is designed to operate a maximal pressure drop and a maximal tube wall temperature. When either limit is reached, the reactor can be operated in a decoking mode to at least partially remove the coke. It is desirable to reduce coke formation and deposition in order to extend the run-lengths of normal operations and minimize decoking frequency.

Reducing radiant section external wall temperature during normal operation of the reactor favors the reduction of coke formation, however, inhibits conversion of the aliphatic hydrocarbons in the radiant section because of the highly endothermal nature of the reactions, and the selectivity toward desired products especially olefins in the radiant section. Conversion and selectivity can be increased by increasing the temperature of the fluid stream in at least a portion of the external surface piping, e.g., the cross-over section and radiant section inlet piping, such that a significant level of thermal cracking reactions occur before the radiant section, making it possible to reduce temperature of the radiant tubes without sacrificing the overall conversion and selectivity toward desirable products.

As used herein, the term “decoking interval” refers to the run-length of the operation of a steam cracking furnace between two adjacent decoking sessions of the furnace. By using electrical heating device(s) to heat the external surface piping, the decoking interval of a steam cracking furnace can be extended by, e.g., from 1%, 2%, 3%, 4%, 5%, to 6%, 7%, 8%, 9%, 10%, to 20%, 30%, 40%, 50%, to 60%, 70%, 80%, 90%, or 100%, compared to a conventional process without using an electrical heating device to heat any external furnace piping.

The processes of this disclosure can further include operating the steam cracker furnace in a decoking mode, in which a decoking fluid is fed into the radiant section. The decoking mode can include an online decoking operation or an offline decoking operation. In a decoking mode, electric power can be supplied to at least one electrical heating device capable of providing heat energy to a segment of the radiant section inlet piping, such as multiple segments of the radiant section inlet piping, thereby increasing the temperature of the fluid passing through the radiant tubes subjected to coke removal and facilitating coke removal in the decoking mode. In a preferred embodiment, multiple, separately controllable and adjustable electrical heating devices (e.g., 123 and 127) are installed to provide heating power to multiple segments of the radiant inlet piping 120 connected to separate radiant tubes (104 a, 104 b, . . . ) as described above and illustrated in FIG. 1 . The radiant tubes may have differing degree of coking at the beginning of the decoking mode. In such case, more heating power may be supplied by the electrical heating device coupled to a segment of the radiant inlet piping that is connected to a radiant tube with a higher degree of coking, preferentially raising the temperature of the fluid in that radiant tube with a higher degree of coking to a higher level, to achieve a faster decoking rate in that radiant tube.

Steam cracking using electric heating in addition to fuel combustion disclosed herein can reduce the amount of fuel gas combusted at the burners, thereby reducing the amount of CO₂-containing flue gas that is otherwise emitted to the environment. Temperature control of the fluids in the various sections in the furnace is possible using the electrical heating device without the need to adjust energy output from the burners. Capacity of existing furnaces can be increased by coupling electric heater devices at one or more locations of the external furnace piping. For a steam cracker furnace limited by fan capacity, environmental permitting of flue gas side emissions, or where it is desirable to a given unit of site to supplement unit capacity with electrical power from a lower emission source, this invention is particularly advantageous.

Full electrification of a steam cracking furnace, i.e., operating a steam cracking furnace using electricity as the sole energy source without using a fuel gas to provide the thermal energy required for steam cracking of the hydrocarbon-containing feed, has been proposed. Such proposals have the following changes, to name a few: (i) development of electrical technology to heat radiant section effluent to the high temperatures required for steam cracking retrofitting existing steam cracking furnaces with such electrical technology; (ii) economics of cost per unit production of chemical must be equivalent or superior to existing fuel fired technology; (iii) amount of power capacity required for a commercial steam cracking furnace must be available in the global renewable energy supply to truly reduce emissions.

The most difficult to overcome is the relationship between the quantity of power required for a commercial electrical steam cracking and the cost of building a facility to provide such power. The likely amount of capital required to construct an electrical facility and world-scale ethylene facility will be exceedingly high compared to its competitors based on today's technology. Comparing the required power input the final user would need to either construct or procure the power from a nearly full sized natural gas power plant. The duty required in the radiant section alone approaches the average power plant under planned construction in the United States for 8 furnaces of radiant duty.

What is needed is a means for increasing steam cracking furnace capacity without increasing greenhouse gas emissions. The processes of this disclosure are deployable on a faster timeline allowing for increased steam cracking capacity using electrical power, which may be procured from renewable sources as available. The processes of this disclosure can be conveniently retrofit into an existing conventional steam cracking furnace to achieve the very many benefits as described above without incurring prohibitive costs.

The Hydrocarbon-Containing Feed

The process of the present disclosure can be used for the conversion of various types of hydrocarbon-containing feed, such as those rich in aliphatic hydrocarbons, into lighter hydrocarbons rich in olefins. In some embodiments, the hydrocarbon-containing feed fed into the furnace can contain ethane as a major component. For example, the hydrocarbon-containing feed can contain from about 50 wt % to about 100 wt % of ethane, such as about 55 wt % to about 99 wt %, such as about 60 wt % to about 90 wt %, such as about 70 wt % to about 85 wt %, such as about 75 wt % to about 80 wt %, based on the total weight of the hydrocarbon-containing feed.

In some embodiments, the hydrocarbon-containing feed fed into the furnace can contain naphtha as a major component. As used herein, “naphtha” means a mixture of C5-C10 aliphatic hydrocarbons. For example, the hydrocarbon-containing feed can contain from about 50 wt % to about 100 wt % of naphtha, such as about 55 wt % to about 99 wt %, such as about 60 wt % to about 90 wt %, such as about 70 wt % to about 85 wt %, such as about 75 wt % to about 80 wt %, based on the total weight of the hydrocarbon-containing feed.

In some embodiments, the hydrocarbon-containing feed fed into the furnace can contain gas oil. As used herein, “gas oil” refers to a mixture of C10-C20 hydrocarbons. A gas coil can contain at least 50 wt % of C10-C20 alkanes. In some embodiments, the fresh hydrocarbon-containing feed can contain from about 50 wt % to about 100 wt % of gas oil, such as about 55 wt % to about 99 wt %, such as about 60 wt % to about 90 wt %, such as about 70 wt % to about 85 wt %, such as about 75 wt % to about 80 wt %, based on the total weight of the hydrocarbon-containing feed.

The Steam Cracking Conditions

The cracking conditions are selected to favor the thermal pyrolysis of the aliphatic hydrocarbon molecules in the feed material to produce smaller, unsaturated hydrocarbon molecules and hydrogen in the cracked fluid mixture. The unsaturated hydrocarbons are further processed into other finished products such as polymers. Preferred steam cracking conditions for differing hydrocarbon-containing feeds are described in U.S. Pat. No. 10,315,968 B2, the relevant contents of which are incorporated herein by reference.

Listing of Embodiments

This disclosure can further include the following non-limiting aspects and/or embodiments:

A1. A steam cracking process comprising:

-   -   (I) providing a steam cracking furnace comprising a furnace         enclosure, a plurality of burners housed in the furnace         enclosure capable of supplying thermal energy by combusting a         fuel, a hydrocarbon-containing feed inlet tube located outside         of the furnace enclosure capable receiving a         hydrocarbon-containing feed, a convection section located inside         the furnace enclosure and coupled to the hydrocarbon-containing         feed inlet tube, a cross-over section located outside of the         furnace enclosure and coupled to an end of the convection         section, a radiant section located inside the furnace enclosure         and coupled to an end of the cross-over section via a radiant         section inlet piping, a radiant section outlet piping coupled to         the radiant section and located outside of the furnace         enclosure, and one or more electrical heating devices capable of         providing heat energy to an external furnace piping selected         from: a segment of the hydrocarbon-containing feed inlet tube, a         segment of the cross-over section, a segment of the radiant         section inlet piping, and a segment of the radiant section         outlet piping, and combinations thereof; wherein the radiant         section inlet piping is located outside of the furnace         enclosure;     -   (II) combusting the fuel at the plurality of the burners to         provide thermal energy to the radiant section and the convection         section;     -   (III) supplying electrical power to at least one of the one or         more electrical heating devices to provide heat energy to the         external furnace piping; and     -   (IV) in a cracking mode, feeding the hydrocarbon-containing feed         through the hydrocarbon-containing feed inlet tube and         optionally water and/or steam into the steam cracking furnace,         heating the hydrocarbon-containing feed and/or the water/steam         in the convection section to obtain a heated feed mixture,         transferring the heated feed mixture from the convection section         to the radiant section via the cross-over section and the         radiant section inlet piping, cracking a plurality of         hydrocarbons in the heated feed mixture in the radiant section         to produce a cracked mixture exiting the steam cracking furnace         through the radiant section outlet piping.

A2. The process of A1, wherein in step (III), a temperature of the segment of the external furnace piping is raised by deltaT ° C. by the heat energy provided by the at least one of the one or more electrical heating devices, where deltaT ranges from 10° C. to 200° C.

A3. The process of A1 or A2, wherein at least one, preferably all, of the one or more electrical heating devices comprise a resistor separate from the external furnace piping, and the resistor receives at least a portion of the electrical power and provides heat energy by resistive heating which is transferred to the external furnace piping.

A4. The process of A3, wherein the resistor is electrically insulated from the external furnace piping.

A5. The process of any of A1 to A4, wherein the at least one of the one or more electrical heating devices comprises a portion of the external furnace piping, at least a portion of the electrical power is supplied to the external furnace piping generating an electric current flowing through the external furnace piping to generate heat energy in the external furnace piping.

A6. The process of any of A1 to A5, wherein at least one of the one or more electrical heating devices provides heat energy to the external furnace piping by induction heating.

A7. The process of A5, wherein the induction heating is at least partly effected by inducing an electric current in the external furnace piping.

A8. The process of any of A1 to A7, wherein at least one of the one or more electrical heating devices provides heat energy by radiant heating.

A9. The process of any of A1 to A8, wherein at least one, preferably all, of the one or more electrical heating devices takes a form of a heating jacket at least partly at least partly enclosing the external furnace piping.

A10. The process of any of A1 to A9, further comprising:

-   -   (V) adjusting the electrical heating power of at least one of         the one or more electrical heating devices to adjust the         temperature of the external furnace piping.

A11. The process of any of A1 to A10, further comprising:

-   -   (VI) monitoring a temperature of the external furnace piping;         and     -   (VII) in steps (III) and (IV) and optionally (V), maintaining         the temperature of the external furnace piping in a range from         T(target)−25° F. to T(target)+25° F., where T(target) is a         predetermined target temperature of the external furnace piping.

A12. The process of any of A1 to A11, wherein the one or more electrical heating devices include at least one electrical heating device providing heat energy to a segment of the cross-over section.

A13. The process of A12, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the cross-over section.

A14. The process of A12 or A13, further comprising controlling and adjusting the electrical heating power of the at least one electrical heating devices to control and/or adjust the temperature of the cross-over section.

A15. The process of any of A12 to A14, wherein a hydrocarbon-containing fluid passing through the cross-over section is heated by the segment of the cross-over section heated by the one or more electrical heating devices, and the hydrocarbon-containing fluid undergoes substantial cracking in the cross-over section.

A16. The process of A15, wherein the hydrocarbon-containing fluid has a temperature at the beginning of the cross-over section such that no substantial hydrocarbon cracking occurs at the beginning of the cross-over section.

A17. The process of A15 or A16, wherein the hydrocarbon-containing fluid has a temperature T1 at the beginning of the cross-over section, the hydrocarbon-containing fluid has a temperature T2 at the end of the cross-over section, and 0° C.<T2−T1≤200° C.

A18. The process of any of A10 to A16, wherein the thermal energy supplied from the plurality of burners is reduced compared to a comparative process conducted in the same steam cracking furnace with an identical conversion of the predominant hydrocarbon in the hydrocarbon-containing feed in step (IV), but without supplying electric power to the electrical heating device capable of providing heat to the cross-over section.

A19. The process of A18, wherein a temperature of a fluid in the radiant section is lower than in the comparative process.

A20. The process of any of A1 to A19, wherein the one or more electrical heating devices include an electrical heating devices providing heat energy to a segment of the radiant section inlet piping.

A21. The process of A20, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the radiant section inlet piping.

A22. The process of A21, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section inlet piping, and the process further comprises separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping, thereby separately controlling and/or adjusting the temperatures of multiple radiant tubes.

A23. The process of any of A1 to A22, wherein the one or more electrical heating devices include an electrical heating devices providing heat energy to a segment of radiant section outlet piping.

A24. The process of A23, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the radiant section outlet piping.

A25. The process of A23 or A24, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section outlet piping, and the process further comprises separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section outlet piping.

A26. The process of any of A1 to A25, wherein the radiant section outlet piping comprises a transfer line tube segment coupled at an end thereof with a transfer line heat exchanger and/or a quenching device, and the one or more electrical heating devices include an electrical heating device capable of being supplied with electrical power and capable of providing heat energy to the transfer line tube segment.

A27. The process of A26, wherein a fluid stream passing through the transfer line tube segment is maintained in a range from T(COT)−25° F. to T(COT)+25° F., where T(COT) is a predetermined temperature.

A28. The process of A26, wherein a fluid stream passing through the transfer line tube segment has a temperature from 15° C. to 200° C. higher than in a comparative process differing from the process only in that electrical power is not supplied to the one or more electrical heating devices capable of providing heat energy to the radiant section outlet piping and the transfer line tube.

A29. The process of any of A1 to A28, further comprising

-   -   (VIII) in a decoking mode, feeding a decoking fluid into the         radiant section;     -   wherein step (III) comprises supplying electric power to at         least one electrical heating device capable of providing heat         energy to a segment of the radiant section inlet piping.

A30. The process of A29, wherein step (III) comprises supplying electric power to multiple electrical heating devices capable of providing heat energy to multiple segments of the radiant section inlet piping.

A31. The process of A30, further comprising separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping.

A32. The process of A31, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section inlet piping, and the process further comprises separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping depending on the degree of coking inside the radiant tubes.

A33. The process of A32, wherein more heating power is provided by an electrical heating device to a segment of the radiant section inlet piping coupled to a radiant tube with higher degree of coking.

A34. The process of any of A29 to A33, wherein the decoking mode includes an online decoking operation.

A35. The process of any of A29 to A34, wherein the decoking mode includes an offline decoking operation.

B1. A steam cracking furnace comprising: a furnace enclosure; a plurality of burners housed in the furnace enclosure capable of supplying thermal energy by combusting a fuel; a hydrocarbon-containing feed inlet tube located outside of the furnace enclosure capable receiving a hydrocarbon-containing feed; a convection section located inside the furnace enclosure and coupled to the hydrocarbon-containing feed inlet tube; a cross-over section located outside of the furnace enclosure and coupled to an end of the convection section; a radiant section located inside the furnace enclosure and coupled to an end of the cross-over section via a radiant section inlet piping, wherein the radiant section inlet piping is located outside of the furnace enclosure; a radiant section outlet piping coupled to the radiant section and located outside of the furnace enclosure; and one or more electrical heating devices capable of, when supplied with electrical power, providing heat energy to an external furnace piping selected from: a segment of the hydrocarbon-containing feed inlet tube, a segment of the cross-over section, a segment of the radiant section inlet piping, and a segment of the radiant section outlet piping, and combinations thereof.

B2. The steam cracking furnace of B1, wherein at least one, preferably all, of the one or more electrical heating devices comprise a resistor separate from the external furnace piping, and the resistor is capable of receiving at least a portion of the electrical power to provide heat energy by resistive heating.

B3. The steam cracking furnace of B2, wherein the resistor is electrically insulated from the external furnace piping.

B4. The steam cracking furnace of B1, wherein the at least one of the one or more electrical heating devices comprises a portion of the external furnace piping, at least a portion of the electrical power is capable of being supplied to the external furnace piping generating an electric current flowing through the external furnace piping to provide heat energy to the external furnace piping.

B5. The steam cracking furnace of B1, wherein at least one of the one or more electrical heating devices is capable of providing heat energy to the external furnace piping by induction heating.

B6. The steam cracking furnace of B5, wherein the at least one of the one or more electrical heating devices is capable of inducing an electric current in the external furnace piping.

B7. The steam cracking furnace of any of B1 to B6, wherein at least one of the one or more electrical heating devices provides heat energy by radiant heating.

B8. The steam cracking furnace of any of B1 to B7, wherein at least one, preferably all, of the one or more electrical heating devices takes a form of a heating jacket at least partly enclosing the external furnace piping.

B9. The steam cracking furnace of any of B1 to B8, wherein the electrical heating power of at least one of the one or more electrical heating devices is adjustable and/or controllable.

B10. The steam cracking furnace of any of B1 to B9, further comprising: a temperature-monitoring device capable of determining a temperature of the external furnace piping; and a controller capable of controlling and/or adjusting the heating power of at least one of the one or more electrical heating devices based on the temperature of the external furnace piping determined by the temperature-monitoring device.

B11. The steam cracking furnace of any of B1 to B10, wherein the one or more electrical heating devices include at least one electrical heating device capable of providing heat energy to a segment of the cross-over section.

B12. The steam cracking furnace of B11, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the cross-over section.

B13. The steam cracking furnace of any of B1 to B12, further comprising: a temperature-monitoring device capable of determining a temperature of a segment of the cross-over section; and a controller capable of controlling and/or adjusting the heating power of at least one of the one or more electrical heating devices based on the temperature of the segment of the cross-over section determined by the temperature-monitoring device.

B14. The steam cracking furnace of any of B1 to B13, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the radiant section inlet piping.

B15. The steam cracking furnace of B14, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section inlet piping, and the steam cracking furnace further comprises a controller capable of separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping, thereby separately controlling and/or adjusting the temperatures of multiple radiant tubes.

B16. The steam cracking furnace of any of B1 to B15, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the radiant section outlet piping.

B17. The steam cracking furnace of B16, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section outlet piping, and the steam cracking furnace further comprises a controller capable of separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section outlet piping.

B18. The steam cracking furnace of any of B1 to B17, wherein the radiant section outlet piping comprises a transfer line tube segment coupled at an end thereof with a transfer line heat exchanger and/or a quenching device, and the one or more electrical heating devices include an electrical heating device capable of being supplied with electrical power and capable of providing heat energy to the transfer line tube segment.

B19. The steam cracking furnace of B18, wherein the steam cracking furnace further comprises a controller capable of controlling and/or adjusting the electrical heating power of the electrical heating devices capable of providing heat energy to the transfer line tube segment.

C1. A second aspect of this disclosure relates to process for steam cracking a hydrocarbon-containing feed, the process comprising one or more of the following:

-   -   (I) providing a steam cracking furnace comprising one or more of         the following: a furnace enclosure, a plurality of burners         housed in the furnace enclosure capable of supplying thermal         energy by combusting a fuel, a hydrocarbon-containing feed inlet         tube located outside of the furnace enclosure capable receiving         a hydrocarbon-containing feed, a convection section located         inside the furnace enclosure and coupled to the         hydrocarbon-containing feed inlet tube, a cross-over section         located outside of the furnace enclosure and coupled to an end         of the convection section, a radiant section located inside the         furnace enclosure and coupled to an end of the cross-over         section via a radiant section inlet piping, a radiant section         outlet piping coupled to the radiant section and located outside         of the furnace enclosure, and one or more electrical heating         devices capable of providing heat energy to an external furnace         piping selected from: a segment of the hydrocarbon-containing         feed inlet tube, a segment of the cross-over section, a segment         of the radiant section inlet piping, and a segment of the         radiant section outlet piping, and combinations thereof; wherein         the radiant section inlet piping is located outside of the         furnace enclosure;     -   (II) combusting the fuel at the plurality of the burners to         provide thermal energy to the radiant section and the convection         section;     -   (III) supplying electrical power to at least one of the one or         more electrical heating devices to provide heat energy to the         segment of the external furnace piping; and     -   (VIII) in a decoking mode, feeding a decoking fluid into the         radiant section; wherein step (III) comprises supplying electric         power to at least one electrical heating device capable of         providing heat energy to a segment of the radiant section inlet         piping. 

What is claimed is:
 1. A process for steam cracking a hydrocarbon-containing feed, the process comprising: (I) providing a steam cracking furnace comprising a furnace enclosure, a plurality of burners housed in the furnace enclosure capable of supplying thermal energy by combusting a fuel, a hydrocarbon-containing feed inlet tube located outside of the furnace enclosure capable receiving a hydrocarbon-containing feed, a convection section located inside the furnace enclosure and coupled to the hydrocarbon-containing feed inlet tube, a cross-over section located outside of the furnace enclosure and coupled to an end of the convection section, a radiant section located inside the furnace enclosure and coupled to an end of the cross-over section via a radiant section inlet piping, a radiant section outlet piping coupled to the radiant section and located outside of the furnace enclosure, and one or more electrical heating devices capable of providing heat energy to an external furnace piping selected from: a segment of the hydrocarbon-containing feed inlet tube, a segment of the cross-over section, a segment of the radiant section inlet piping, and a segment of the radiant section outlet piping, and combinations thereof; wherein the radiant section inlet piping is located outside of the furnace enclosure; (II) combusting the fuel at the plurality of the burners to provide thermal energy to the radiant section and the convection section; (III) supplying electrical power to at least one of the one or more electrical heating devices to provide heat energy to the segment of the external furnace piping; and (IV) in a cracking mode, feeding the hydrocarbon-containing feed through the hydrocarbon-containing feed inlet tube and optionally water and/or steam into the steam cracking furnace, heating the hydrocarbon-containing feed and/or the water/steam in the convection section to obtain a heated feed mixture, transferring the heated feed mixture from the convection section to the radiant section via the cross-over section and the radiant section inlet piping, cracking a plurality of hydrocarbons in the heated feed mixture in the radiant section to produce a cracked mixture exiting the steam cracking furnace through the radiant section outlet piping.
 2. The process of claim 1, wherein in step (III), a temperature of the segment of the external furnace piping is raised by deltaT ° C. by the heat energy provided by the at least one of the one or more electrical heating devices, where deltaT ranges from 10° C. to 200° C.
 3. The process of claim 1, wherein at least one, preferably all, of the one or more electrical heating devices comprise a resistor separate from the external furnace piping, and the resistor receives at least a portion of the electrical power and provides heat energy by resistive heating which is transferred to the external furnace piping.
 4. The process of claim 1, wherein at least one of the one or more electrical heating devices provides heat energy to the external furnace piping by induction heating.
 5. The process of claim 1, wherein at least one of the one or more electrical heating devices provides heat energy by radiant heating.
 6. The process of claim 1, wherein at least one, preferably all, of the one or more electrical heating devices takes a form of a heating jacket at least partly at least partly enclosing the external furnace piping.
 7. The process of claim 1, further comprising: (V) adjusting the electrical heating power of at least one of the one or more electrical heating devices to adjust the temperature of the external furnace piping.
 8. The process of claim 1, further comprising: (VI) monitoring a temperature of the external furnace piping; and (VII) in steps (III) and (IV) and optionally (V), maintaining the temperature of the external furnace piping in a range from T(target)−15° C. to T(target)+15° C., where T(target) is a predetermined target temperature of the external furnace piping.
 9. The process of claim 1, wherein the one or more electrical heating devices include at least one electrical heating device providing heat energy to a segment of the cross-over section.
 10. The process of claim 9, wherein the one or more electrical heating devices include multiple electrical heating devices capable of being separately supplied with electrical power and capable of providing heat energy separately to multiple segments of the cross-over section.
 11. The process of claim 9, further comprising controlling and adjusting the electrical heating power of the at least one electrical heating devices to control and/or adjust the temperature of the cross-over section.
 12. The process of claim 1, wherein the one or more electrical heating devices include an electrical heating devices providing heat energy to a segment of the radiant section inlet piping.
 13. The process of claim 12, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section inlet piping, and the process further comprises separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping, thereby separately controlling and/or adjusting the temperatures of multiple radiant tubes.
 14. The process of claim 1, wherein the one or more electrical heating devices include an electrical heating devices providing heat energy to a segment of radiant section outlet piping.
 15. The process of claim 14, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section outlet piping, and the process further comprises separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section outlet piping.
 16. The process of claim 1, wherein the radiant section outlet piping comprises a transfer line tube segment coupled at an end thereof with a transfer line heat exchanger and/or a quenching device, and the one or more electrical heating devices include an electrical heating device capable of being supplied with electrical power and capable of providing heat energy to the transfer line tube segment.
 17. The process of claim 14, wherein a fluid stream passing through the transfer line tube segment is maintained in a range from T(COT)−15° C. to T(COT)+15° C., where T(COT) is a predetermined temperature.
 18. The process of claim 16, wherein a fluid stream passing through the transfer line tube segment has a temperature from 15° C. to 200° C. higher than in a comparative process differing from the process only in that electrical power is not supplied to the one or more electrical heating devices capable of providing heat energy to the radiant section outlet piping and the transfer line tube.
 19. The process of claim 1, further comprising (VIII) in a decoking mode, feeding a decoking fluid into the radiant section; wherein step (III) comprises supplying electric power to at least one electrical heating device capable of providing heat energy to a segment of the radiant section inlet piping.
 20. The process of claim 19, wherein step (III) comprises supplying electric power to multiple electrical heating devices capable of providing heat energy to multiple segments of the radiant section inlet piping.
 21. The process of claim 20, further comprising separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping.
 22. The process of claim 21, wherein the radiant section comprises multiple radiant tubes coupled separately to the multiple segments of the radiant section inlet piping, and the process further comprises separately controlling and/or adjusting the electrical heating power of the multiple electrical heating devices to separately control and/or adjust the temperatures of the multiple segments of the radiant section inlet piping depending on the degree of coking inside the radiant tubes.
 23. The process of claim 22, wherein more heating power is provided by an electrical heating device to a segment of the radiant section inlet piping coupled to a radiant tube with higher degree of coking.
 24. The process of claim 19, wherein the decoking mode includes an online decoking operation.
 25. The process of claim 19, wherein the decoking mode includes an offline decoking operation.
 26. A process for steam cracking a hydrocarbon-containing feed, the process comprising one or more of the following: (I) providing a steam cracking furnace comprising: a furnace enclosure, a plurality of burners housed in the furnace enclosure capable of supplying thermal energy by combusting a fuel, a hydrocarbon-containing feed inlet tube located outside of the furnace enclosure capable receiving a hydrocarbon-containing feed, a convection section located inside the furnace enclosure and coupled to the hydrocarbon-containing feed inlet tube, a cross-over section located outside of the furnace enclosure and coupled to an end of the convection section, a radiant section located inside the furnace enclosure and coupled to an end of the cross-over section via a radiant section inlet piping, a radiant section outlet piping coupled to the radiant section and located outside of the furnace enclosure, and one or more electrical heating devices capable of providing heat energy to an external furnace piping selected from: a segment of the hydrocarbon-containing feed inlet tube, a segment of the cross-over section, a segment of the radiant section inlet piping, and a segment of the radiant section outlet piping, and combinations thereof; wherein the radiant section inlet piping is located outside of the furnace enclosure; (II) combusting the fuel at the plurality of the burners to provide thermal energy to the radiant section and the convection section; (III) supplying electrical power to at least one of the one or more electrical heating devices to provide heat energy to the segment of the external furnace piping; and (VIII) in a decoking mode, feeding a decoking fluid into the radiant section; wherein step (III) comprises supplying electric power to at least one electrical heating device capable of providing heat energy to a segment of the radiant section inlet piping. 